Tiltable lifting tongs

ABSTRACT

The specification discloses tiltable lifting tongs of the type having opposing grappling jaws for grasping and releasing a load, such as a coil of sheet steel, and having a power driven cable sling for tilting the tongs through an angle, such as 90*, to correspondingly change the orientation of the load between pickup and set-down thereof. A toggle linkage is employed whereby the load reaction force acting in the cable sling is applied to one of the tong levers controlling the gripping pressure of the grappling jaws in such a manner as to provide an amplification of the forces exerted on the tong lever and also to maintain a substantially constant and near maximum lever arm ratio therefor throughout the entire angle of change in orientation.

United States Patent Siegwart [451 Aug. 1,1972

[73] Assignee: Heppenstall Company, Pittsburgh,

22 Filed: May2l, 1971 21 Appl. No.: 145,716

[52] US. Cl. ..294/103 CG, 214/658 [51] Int. Cl ..B66c 1/22 [58] Field of Search ..294/103, 104, 111, 112; 214/658 [56] References Cited UNITED STATES PATENTS 2,945,609 7/1960 Benes et a1 ..214/658 3,076,674 2/1963 Anderson ..294/103 R 3,436,116 4/1969 Anderson ..294/103 R Primary Examiner-Evon C. Blunk Assistant Examiner-Johnny D. Cherry Attorney-Buell, Blenko & Ziesenheim [5 7 ABSTRACT The specification discloses tiltable lifting tongs of the type having opposing grappling jaws for grasping and releasing a load, such as a coil of sheet steel, and having a power driven cable sling for tilting the tongs through an angle, such as 90, to correspondingly change the orientation of the load between pick-up and set-down thereof. A toggle linkage is employed whereby the load reaction force acting in the cable sling is applied to one of the tong levers controlling the gripping pressure of the grappling jaws in such a manner as to provide an amplification of the forces exerted on the tong lever and also to maintain a substantially constant and near maximum lever arm ratio therefor throughout the entire angle of change in orientation.

5 Claims, 6 Drawing Figures PATENTEDAUG 1 I012 sum 1 [IF 2 FIG.4

TILTABLE LIFTING TONGS This invention relates to tiltable lifting tongs of the type having opposed jaws for grasping and releasing a load, such as a coil of sheet steel or aluminum, and operable to change the orientation of the load between pick-up and set-down.

Tiltable lifting tongs heretofore known, as exemplified by that described in U.S. Pat. No. 3,436,l16issued Apr. 1, 1969 to J. R. Anderson and assigned to the assignee of this invention, are known and used in industries. In the steel industry, by reason of the orientation of strip mills and processing lines, the strip is necessarily coiled on a horizontal axis to form a coil which is ordinarily banded to hold it in the form of a coil. Such coils are of varying weight, and may attain weights as high as one hundred thousand pounds. Although such coils are wound on a horizontal axis because of mill designs, and are wound on a horizontal axis because of mill designs, and are unwound on a horizontal axis for the same reason, the coils are preferably stacked with the coil axis in a vertical position to avoid rolling and possible breaking of the bands.

The tiltable tongs illustrated in U.S. Pat. No. 3,436,116 provided a desirable improvement over the tilting apparatus theretofore employed for the purpose of changing the coils from a horizontal to a vertical orientation.

The existing tiltable tongs are provided with an adjustable outboard tilting leg extension to obtain full capacity or effectiveness of the turning torque designed into the unit. Moreover, variations in the material and gripping areaof the outer gripping shoe may be had to accommodate highly finished or soft material type of coils. The inherent design of the existing tiltable tongs with respect to the manner of application of load reaction force to the tong levers is such, however, that the gripping force on a coil during the transition from horizontal axis orientation to vertical axis orientation may not provide the necessary factor of safety under certain conditions, especially when the operating personnel endeavor to employ the lifting tongs under circumstances where the weight of the coil is excessive in relation to the capacity of the unit, or when the gripping jaws are unsuited to the material of which the coils are made.

I provide means for applying the load reaction force to one of the tong levers controlling the gripping force of the movable grappling jaw so as to intensify the effective gripping force and thereby insure an adequate factor of safety.

More specifically there is provided a toggle linkage by which the load reaction force is applied to the tong lever controlling the gripping force of the movable grappling jaw, thereby to effect an amplification of the force to which the tong lever is subject under minimum load reaction force conditions while limiting to a small amount the increase in the force on the tong lever under conditions of greatest load traction force. Moreover, the lever arm ratio by which the tong lever applies force to the movable grappling jaw is maintained substantially constant throughout the entire angle of change in orientation.

In order to more clearly present the essential structural and operational differences between the invention and the existing tiltable tongs exemplified by the prior design disclosed in U.S. Pat. No. 3,436,116, simplified views of the prior design are included in the accompanying drawings, wherein:

FIGS. 1, 2 and 3 are elevational views showing tiltable lifting tongs, embodying the invention, in the respective positions assumed by the unit with the axis of the coil in a horizontal, an inclined and a vertical position; and

FIGS. 4, 5 and 6 are elevational views showing tiltable lifting tongs of the prior design in positions corresponding respectively to the positions shown in FIGS. 1, 2 and 3.

In view of the fact that in large part, the internal details of the tiltable lifting tongs embodying the invention and the tiltable lifting tongs of the prior design are substantially alike, it should be understood that corresponding reference numerals will be hereinafter employed in FIGS. 1 and 4 to designate corresponding elements therein, without repeating the description of the prior art design itself. Except as pointed out hereinafter, reference numerals are omitted from FIGS. 2, 3, 5 and 6 for simplicity and avoidance of unnecessary repetition.

Referring now to FIGS. 1 and 4, the common elements of the tiltable lifting tongs shown therein will now be briefly described, it being understood that reference to U.S. Pat. No. 3,436,116 may be had for complete structural details. and description of the unit. For convenience, the same reference numerals are used herein, as are used in the patent, to identify a corresponding element. The unit is generally designated by reference numeral 10 and includes a grappling arm portion 12 having a rigid base member 14 made up of two laterally spaced parallel angle plates 15, only one of which is shown. Base member 14 supports an inner grappling jaw 16 which is suitably fixed thereto. An outer grappling jaw 17 is supported by base member 14 in spaced relation to the inner jaw 16 and is reciprocatively movable with respect thereto for gripping therebetween the wall of a coil 18 of sheet steel.

Outer jaw 17 is pivotally mounted on one end of an L-shaped grappling arm 20, made up of two parallel spaced plates. The other end of the arm 20 extends between the plates 15 of base member 14 and is suitably slidably arranged therein.

Contained within a housing member 41 detachably fixed to the base member 14 is a power drive assembly including a reversible electric motor (not shown). The power drive assembly also includes a screw and nut arrangement via which movement of the outer grappling jaw 17 with respect to the inner jaw 16 is effected.

A generally L-shaped lever arm 50, consisting of two laterally spaced identical plates only one of which is shown, has a long leg that extends longitudinally of the base member 14 and to one side of the housing member 41. Lever arm 50 has a short leg that is pivotally connected to a thrust block (not shown), at a point designated by the reference numeral 51, the thrust block in turn being slidably supported by a key and slot arrangement between the two side plates of grappling arm 20. The long leg of lever arm 50 is connected by a link member 54, comprising two identical laterally spaced plates, to the base member 14. One end of the link 54 is pivotally connected to the base member and the other end is pivotally connected to the lever arm by a pin 56 which slides in a longitudinally extending closed slot 55 adjacent the end of the two side plates of link 54. Slots'55 define the limits of movement of lever arm 50 relative to the base member 14.

Lever arm 50 has a main pivot pin 53 by which a pivotal connection is formed with a support arm 57. Support arm 57 comprises two laterally spaced L- shaped plates, one of which is shown. Each of the side plates of support arm 57 has an arm fixed to the inner face of a corresponding one of the angle plates forming base member 14. Each of the side plates of support arm 57 also has a leg transverse to the base member and paralleling the movable grappling jaw 17. Suitably secured, as by a key and slot arrangement, between the side plates of the support arm 57 is an adjustable extension member 66.

Disposed above the grappling arm portion 12 of the lifting tongs assembly 10 is a suspending means 74 in the form of a power-driven sling arrangement. Suspending means 74 comprises a housing which includes two laterally spaced generally triangular plates 78, only one of which is shown. At the upper end of plates 78 are coaxial openings in which a tubular generally cylindrical shaped spool 80 is fixedly supported. Spool 80 is necked at its midpoint between plates 78 to accommodate a crane hook 83.

Suitably mounted externally with respect to the plates 78 are a pair of toothed drive sprockets 96, only one of which is shown. Sprockets 96 are keyed to opposite ends of the output shaft of a speed reducer (not shown) which is, in turn, driven by a reversible electric motor (not shown). The speed reducer and the electric motor are suitably mounted between the plates 78 in parallel relation to each other and operatively connected as specifically described in US. Pat. No. 3,436,116.

Rotatably mounted externally of each of the plates 78 are a pair of identically shaped idler sprockets 102, in laterally spaced coplanar relation to each other and with respect to the drive sprocket 96 on the corresponding side of the suspension means housing plates Referring now only to the prior design shown in FIG. 4, a pair of identical roller chains 107 are provided by which to suspend the grappling portion assembly from the suspension means, one chain for each side of the suspension means. Since the connections and path of each roller chain 107 are in parallel and similar, only the connections and path for one chain will be here described. Thus, one end of a chain 107 is suitably connected to the end of the extension member 66 on support arm 57, thence it is reaved around the inner surface of one idler sprocket 102, over the drive sprocket 96, and returning back on the inner side of the second idler sprocket 102 and outwardly of the suspension means, over a support shaft or pin 71 on the support arm 57, and back to the end of lever arm 50 where it is suitably pivotally anchored.

While not apparent in the drawings, it should be understood that in addition to the roller chains 107, there are provided a pair of identical wire ropes similarly connected at opposite ends to support arm 57 and lever arm 50 and reaved around pulleys coaxially mounted and keyed to the same shafts as the sprockets 102 and 96.

Referring to FIG. 1, the modifications made in the prior design of tiltable lifting tongs, according to the in vention, will now be described. A so-called toggle link 110 is provided between the base member 14 and the free outer end of lever arm 50. Toggle link 110 comprises two arms 111 and 112, each arm consisting of two laterally spaced parallel elements only one of which is shown. Arms 111 and 112 are pivotally connected together by a suitable hinge pin 113 extending through cooperating ends thereof. The other end ,of arm 111 is pivotally connected by a suitable pin to a clevis bracket 114 attached to base member 14. The other end of arm 112 is pivotally connected, as by a suitable pin-1 15, to the outer end of lever arm 50.

A pair of roller chains 107 and wire cables (not shown) are provided by which to suspend the grappling portion assembly, in a manner similar to that described for the prior design of FIG. 4. However, as shown in FIGS. 1, 2 and 3, the one end of roller chains 107 and of counterpart wire cables are connected pivotally to the hinge pin 113 coupling the two arms of toggle link 1 10. The advantages obtained by this manner of applying the load reaction force in roller chains 107 and their counterpart wire cables to the lever arm 50 will be demonstrated hereinafter by a comparison of the forces applied to lever arm 50 and the leverage ratio applicable in each of the different positions of the lifting tong unit for the prior design of unit and for the unit constructed according to the invention.

In order to explain the meaning of the term leverage ratio the moment arm for the load reaction force effective on the lever arm 50 is designated by the reference letter D and shown in each of the Figures of the drawings. Similarly, the moment arm of the gripping force applied to grappling jaw 17 is designated by the reference letter d and shown in each of the Figures.

Referring to FIG. 4, the force moments active may be expressed by the equation:

F,, X D +f;, X d 1 where F is the load reaction force and f, is the gripping force exerted by the grappling jaw 17;

By transposition:

The term leverage ratio as used herein refers to the ratio of the moment arms D and d. As will be evident from equation (2), therefore, the gripping force exerted by the grappling jaw 17 is proportional to the leverage ratio D/d.

It will be understood that the connection of the roller chain 107 and wire cables to the toggle link 110 causes an amplification of the force effectively exerted by the load reaction force on the lever arm 50, by reason of the relatively greater component of force applied norma] to lever arm 50 instead of longitudinally thereof as in the case of the prior design shown in FIGS. 4, 5 and 6.

Referring now to FIGS. 4, 5 and 6, it will be apparent by inspection of the relative lengths of moment arms D and d in these Figures that in FIGS. 4 and 5 the leverage ratio D/d is approximately equal to 1, whereas in FIG. 6 the leverage ratio D/d is equal to a multiple of 1. Thus in the prior design of tilting lifting tongs, the leverage ratio D/d does not begin to increase greatly over 1 until the inclination of the axis of coil 18 approaches the vertical position shown in FIG. 6. There is therefore a critical angle of inclination of the axis of coil 18 in which the leverage ratio D/d is sufiiciently low that, under certain conditions, the gripping force f, exerted by the grappling jaw 17 may not hold the weight of the coil 18 against possible slippage with a sufiiciently high safety factor.

Referring now to FIGS. 1, 2 and 3, it will be apparent .by inspection of the relative lengths of moment arms D and d, that the leverage ratio D/d is a multiple of 1 regardless of the orientation of the axis of coil 18. Moreover, the leverage ratio D/d is a substantially uniform value starting with the horizontal position of the axis of the coil 18, through all angles of inclination of the coil axis up to and including the vertical position of the coil axis shown in FIG. 3. It will be seen also that notwithstanding the change in orientation of the coil axis, the resultant of the forces exerted on the end of tong lever 50 via the toggle link 110 by the load reaction forces F applied to the knee of the toggle link is greater than the load reaction force itself, beginning with the horizontal position of the axis of coil 18 in FIG. 1 and continuing through the various inclined positions of the coil axis, as represented in FIG. 2, up to and including the vertical position of the coil axis shown in FIG. 3.

It will be seen, therefore, that by providing the arrangement of toggle link 110 by which the load reaction force is applied to lever arm 50, the possibility of a critical angle at which slippage of the grip of the grappling jaws l6 and 17 on the wall of coil 18 may occur is obviated.

It should be understood that the characteristic essential to operativeness of the toggle link 110 lies in the arms 111 and 112 always remaining at angle to each other which is less than 180, for should the arms 111 and 112 become aligned at 180 or pass such point of alignment the efiective force on the tong lever 50 is lost or even reversed. The slotted link member 54 thus serves the additional function of insuring the maintaining of the arms of the toggle link 110 always at an angle less than 180 by reason of the fact that the length of the slot 55 in the link member 54 prevents sufficient outward movement of the end of lever 50 to allow the arms of the toggle link 110 to reach an aligned position. Thus toggle link 110 remains constantly effectively to exert an amplified component of the load reaction force on the end of lever 50.

In operation, the embodiment of tiltable lifting tongs constructed according to the invention functions in exactly the same manner as the prior design so far as pickup, tilting and release of the coil 18 is concerned. Thus, assuming that the axis of coil 18 is in a horizontal position, pick-up of the coil may be effected by placing the grappling jaws l6 and 17 in straddling relation to the wall of the coil, energizing the motor in housing member 41 to shift grappling jaw 17 toward the fixed jaw 16 to effect a gripping of the wall of the coil, and elevating the suspension means 74 by means of the crane. Upon lift up of the coil 18, the load reaction force effective in the roller chains 107 and paralleling wire cables on the lever arm 50 causes application of substantially the maximum gripping force by grappling jaw 17 to support the coil. Assuming that the coil is now being transported to the desired location for setdown, energization of the tilting motor in the suspension means 74 causes shortening of one end of the roller chains 107 and lengthening of the other end, thereby shifting the coil axis through a substantially angle to the vertical position shown in FIG. 3. Reversal of the motor in housing 41 may be effected to move the grappling jaw 17 away from fixed jaw 16, thus releasing the grip on the coil wall and allowing the lifting tong assembly 10 to be elevated away from the coil.

In conclusion, it will be seen that the tiltable lifting tongs embodying a toggle link whereby the load reaction force is applied to the lever arm of the grappling portion not only provides a greater effective force applicable to the movable grappling jaw for the same weight of load but also maintains a substantially uniform leverage ratio for the grappling portion regardless of the orientation of the axis of the coil being lifted, thereby obviating the possibility of slippage of the grappling jaws on the coil at a critical angle of inclination of the coil axis.

Iclaim:

l. Tiltable lifting tongs comprising a grappling portion having a fixed jaw member and a cooperating jaw member movable with respect to said fixed jaw member to grip a load element therebetween or to release said load element, a support arm,a tong lever pivoted on said support arm so as to activate said movable jaw member, and suspension means including flexible elongated means connected at its opposite ends to said support arm and to said tong lever whereby to support said grappling portion, wherein the improvement comprises toggle linkage interposed between the flexible elongated means and the tong lever.

2. Tiltable lifting tongs according to claim 1, wherein the said grappling portion comprises an elongated base member on which the said support arm is fixed, and wherein said toggle linkage comprises a pair of members, hinged together at an angle less than one member being anchored to said base member and the other member being anchored to said tong lever, the load reaction force in said flexible elongated means being effectively exerted at the hinge of the toggle linkage to intensify the gripping force exerted by the tong lever on the movable jaw member.

3. Tiltable lifting tongs according to claim 2, wherein a slotted link member connected between said base member and said tong lever limits the relative movement of the hinged members so as to maintain the angle between the hinged members always less than 180.

4. Tiltable lifting tongs comprising a grappling portion having a fixed jaw member and a movable jaw member in substantially parallel relation to each other, power means for moving said movable jaw member relative to said fixed jaw member to grip a load element therebetween or to release said load element, a support arm, a tong lever pivoted on said support arm so as to activate said movable jaw member; a suspension portion having flexible elongated means connected at its opposite ends to said support arm and to said tong lever whereby to support said grappling portion, said tong lever being activated responsively to the load reaction force thereon to apply a gripping force to said movable jaw member, and power driven means for shifting said flexible elongated means longitudinally in opposite directions to effect corresponding tilting of the grappling portion and the load supported thereby, wherein the improvement comprises toggle linkage via which the load reaction force in the flexible elongated means is applied to said tong lever.

5. Tiltable lifting tongs according to claim 4, wherein the said grappling portion comprises an elongated base member on which the said support arm is fixed, and wherein the said toggle linkage comprises two members hinged together at an angle less than 180, one of said 

1. Tiltable lifting tongs comprising a grappling portion having a fixed jaw member and a cooperating jaw member movable with respect to said fixed jaw member to grip a load element therebetween or to release said load element, a support arm,a tong lever pivoted on said support arm so as to activate said movable jaw member, and suspension means including flexible elongated means connected at its opposite ends to said support arm and to said tong lever whereby to support said grappling portion, wherein the improvement comprises toggle linkage interposed between the flexible elongated means and the tong lever.
 2. Tiltable lifting tongs according to claim 1, wherein the said grappling portion comprises an elongated base membEr on which the said support arm is fixed, and wherein said toggle linkage comprises a pair of members, hinged together at an angle less than 180* one member being anchored to said base member and the other member being anchored to said tong lever, the load reaction force in said flexible elongated means being effectively exerted at the hinge of the toggle linkage to intensify the gripping force exerted by the tong lever on the movable jaw member.
 3. Tiltable lifting tongs according to claim 2, wherein a slotted link member connected between said base member and said tong lever limits the relative movement of the hinged members so as to maintain the angle between the hinged members always less than 180*.
 4. Tiltable lifting tongs comprising a grappling portion having a fixed jaw member and a movable jaw member in substantially parallel relation to each other, power means for moving said movable jaw member relative to said fixed jaw member to grip a load element therebetween or to release said load element, a support arm, a tong lever pivoted on said support arm so as to activate said movable jaw member; a suspension portion having flexible elongated means connected at its opposite ends to said support arm and to said tong lever whereby to support said grappling portion, said tong lever being activated responsively to the load reaction force thereon to apply a gripping force to said movable jaw member, and power driven means for shifting said flexible elongated means longitudinally in opposite directions to effect corresponding tilting of the grappling portion and the load supported thereby, wherein the improvement comprises toggle linkage via which the load reaction force in the flexible elongated means is applied to said tong lever.
 5. Tiltable lifting tongs according to claim 4, wherein the said grappling portion comprises an elongated base member on which the said support arm is fixed, and wherein the said toggle linkage comprises two members hinged together at an angle less than 180*, one of said members being anchored to said base member and the other of said members being anchored to said tong lever, the flexible elongated means being connected at the hinged connection between said two members, whereby the gripping force exerted by the tong lever on said movable jaw member is intensified and the leverage ratio of the tong lever is maintained at a substantially uniform value and a multiple of 1 throughout the tilting range of movement of the grappling portion. 